The present invention relates to an end seal which is one kind of a sealing device.
As a pressure apparatus provided with an end seal, an accumulator 51 shown in FIG. 9 has been heretofore known, the accumulator being constituted as described below.
That is, first, cover members 54, 55 are welded and secured to opposite ends of a tubular shell 53 to provide a housing 52, the housing 52 housing therein an operating member 56 provided with a bellows 57 and an end member 58. The bellows 57 has one end secured to one cover member 54, and the other end secured to the end member 58, whereby the interior of the housing 52 is divided by the bellows 57 and the end member 58 into an internal gas chamber 59 and an external pressure chamber 60 of the bellows 57 and the end member 58.
One cover member 54 on the left side in the figure is provided with an injection hole 61 for injecting gas into a gas chamber 59, and a plug member 62 for closing the injection hole 61 is mounted on the injection hole 61. Accordingly, the plug member 62 is removed and gas having predetermined pressure is injected into the gas chamber 59from the injection hole 61. After injection, the injection hole 61 is closed by the plug member 62 to thereby seal the gas having predetermined pressure into the gas chamber 59.
Further, the other cover member 55 on the right side in the figure is provided with a mounting portion 63 provided with a thread portion 64 for connecting the accumulator 51 to a pressure pipe such as an oil pressure pipe not shown, and with a pressure introducing port 65 for introducing pressure within the pressure pipe into a pressure chamber 60. Accordingly, the accumulator 51 is connected to the pressure pipe in the mounting portion 63 so that the pressure within the pressure pipe is introduced from the pressure introducing port 65 into the pressure chamber 60.
The accumulator 51 provided with the above-described constitution has a function to absorb a pulsation of pressure generated, for example, in the pressure pipe by keeping the balance between the sealed gas pressure in the gas chamber 59 and the pressure in the pressure chamber 60. However, when the pressure within the pressure chamber 60 during operation, that is, the pressure within the pipe should extremely lower, the bellows 57 is inflated due to a pressure difference between the inside and the outside to possibly be buckled and broken.
Accordingly, in the above-described accumulator 51, measures therefor are taken such that an end seal 66 is mounted on the end of the end member 58 by a baking means so that the pressure in the pressure chamber 60 is not lowered to a level below a predetermined value by the sealing action of the end seal 66. That is, when the pressure in the pressure chamber 60 lowers during operation, the bellows 57 extends so long that the end seal 66 mounted on the end of the end member 58 comes in close contact with an end portion 55a of the other cover member 55, and therefore, the pressure chamber 60 is intercepted from the pressure introducing port 65 by the sealing action of the end seal 66 caused by the close contact. Accordingly, even if the pressure in the pressure pipe further lowers after the interception, the pressure in the pressure chamber 60 is not lowered to thereby keep the balance between the sealed gas pressure in the gas chamber 59 and the pressure in the pressure chamber 60 to prevent the bellows 57 from being inflated.
However, in the above-described conventional accumulator 51, it is set so that the end seal 66 is mounted on the end of the end member 58 as mentioned above, and the end seal 66 is sandwiched between the end portion 55a of the cover member 55 and the end member 58 being moved toward the end portion 55a due to the predetermined pressure difference. Therefore, the end seal 66 is sandwiched between the end portion 55a and the end member 58 in a compressed state to receive large load, which is repeated every expansion and contraction of the bellows 57 resulting from a pressure variation, resulting in an inconvenience that a phenomenon of a permanent set of fatigue occurs relatively early in the end seal 66 whereby the sealing performance of the end seal 66 rapidly lowers.
A first object of the present invention is to improve an end seal for sealing an end of a pressure apparatus such as an accumulator and other apparatuses.
A second object of the present invention is to prevent an early occurrence of a permanent set of fatigue in a seal member.
A third object of the present invention is to provide an end seal capable of securing the stable sealing performance for a long period of time.
A fourth object of the present invention is to provide an end seal having construction in which a seal is hard to be removed from a housing.
An end seal according to one form of the present invention comprises an end seal for sealing between an end portion and an operating member moving toward said end portion. There is a seal member mounted on said end portion. When said operating member comes in contact with said end portion and stops or is stopped by a stopper, a seal lip pressed by sealing fluid pressure into close contact with said operating member is provided on said seal member.
In an end seal according to a further form of the present invention, an annular rigid member is provided on the inner peripheral side of a seal member, and an outer peripheral surface of an extreme end of said rigid member arranged on the inner peripheral side of a seal lip of said seal member is formed in the form of a divergent taper adjusting to a shape of said seal lip.
An end seal according to another form of the present invention comprises an end seal for sealing between an end portion of a housing and an operating member moving toward said end portion. There are provided a seal member inserted in a non-adhesive manner into a recessed seal mounting portion provided on said end portion, and an annular rigid member secured to said housing on the inner peripheral side of said seal member. When said operating member comes in contact with said end portion and stops or is stopped by a stopper, a seal lip pressed by sealing fluid pressure into close contact with said operating member is provided on said seal member. On said rigid member is provided a divergent tapered extreme end positioned on the inner peripheral side of said seal lip to backup said seal lip and to prevent said seal member from slipping out from said seal mounting portion.
In an end seal according to another form of the present invention, a rigid member is inserted into a fluid flow passage provided in a housing, and a difference in-level locating portion provided on the outer peripheral surface of said rigid member runs into a difference in-level locating portion provided on the inner surface of said fluid flow passage to thereby specify the inserting depth of said rigid member.
In an end seal according to still another form of the present invention, a rigid member is inserted into a fluid flow passage provided in a housing, and a proximal end of said rigid member positioned forwardly of an inserting direction is enlarged in diameter after insertion into engagement with said housing to thereby prevent said rigid member for slipping out from said fluid flow passage.
In the above-described end seal, the seal member is mounted not on the operating member on the moving side but on the end portion on the stationary side. Moreover, in a state that the operating member moving toward the end portion comes in contact with the end portion and stops, or is stopped by a stopper separately provided on the end portion, a seal lip of the seal member of said end seal is pressed by the sealing fluid pressure into close contact with the operating member to thereby provide the sealing action. Accordingly, sealing is not done in a state that the seal member is strongly sandwiched between rigid materials but is done in a state that a seal lip of the seal member is in close contact with the already stopped moving member under predetermined contact pressure, thus making it possible to prevent an occurrence of early permanent set of fatigue in the seal member provided with the seal lip.
In the case where the present invention is applied to the accumulator which is a pressure apparatus as described above, the end seal is mounted on the end portion of the housing of the accumulator corresponding to the end portion. In this case, preferably, with respect to materials for the seal member or the seal lip, EPDM or the like is used when a pressure element (sealing fluid or object fluid) introduced into a pressure chamber of the accumulator, and rubber such as NBR is used when it is mineral oil. Further, preferably, with respect to the hardness of the seal member or the seal lip, in consideration of anti-protrusion of the seal lip against high pressure, this is set relatively high.
In addition to the above, in the end seal mentioned above, the outer peripheral surface of the extreme end of the rigid member formed into a divergent taper displays the action for backing up the seal lip to thereby prevent the seal lip from being inverted on the inner peripheral side. Further, the maximum outside-diameter dimension of the outer peripheral surface of the extreme end of the rigid member formed into the divergent taper is set larger than the minimum inside-diameter dimension of the seal member whereby the outer peripheral surface of the extreme end of the rigid member displays the anti-slip action to prevent the seal member from being detached from the mounting portion of the end portion.
In the above-described end seal, the seal member is inserted into not the operating member on the moving side but into the recessed seal mounting portion provided on the end portion of the housing on the stationary side in a non-adhesive manner. Moreover, in the state that the operating member moving toward the end portion comes in contact with the end portion and stops, or is stopped by a stopper separately provided with respect to the end portion, the seal lip of the seal member of the end seal is pressed by the sealing fluid pressure into close contact with the operating member to thereby display the sealing action. Accordingly, the seal member is not sealed in the state that the former is strongly sandwiched between the rigid materials but is sealed in the state that the seal lip of the seal member is in close contact with the already stopped moving member under the predetermined contact pressure, thus making it possible to prevent an occurrence of early permanent set of fatigue in the seal member provided with the seal lip. Furthermore, because the divergent tapered extreme end positioned on the inner peripheral side of the seal lip to back up the seal lip and prevent the seal member from slipping out from the seal mounting portion is provided on the annular rigid member secured to the housing on the inner peripheral side of the seal member, the presence of the tapered rigid extreme end enables prevention of the seal lip from being inverted, and enables prevention of the seal member from being detached from the mounting portion of the housing.
In addition to the above, according to the above-described end seal, the locating action by way of the protrusion between the difference in-level locating portion provided on the outer peripheral surface of the rigid member and the difference in-level locating portion provided on the inner surface of the fluid flow passage enables accurate provision of a height position of the rigid member with respect to the end portion of the housing.
Furthermore, the engaging action of the proximal end of the rigid member enlarged in diameter after insertion enables fixing the rigid member to the housing in a strongly anti-slipped state.